1. Field of the Invention
The present invention relates to an image recording apparatus which ejects ink onto a recording medium while conveying the recording medium by an endless belt to record an image thereon.
2. Description of the Related Art
In general, office automation equipment such as facsimiles, copiers and printers is in wide use. Among the office automation equipment, a recording apparatus of the type which uses cut sheets is equipped with a conveying mechanism. This conveying mechanism conveys the cut sheet from a paper feed section such as a cassette to an image recording section, and then conveys the cut sheet to a paper discharge section after image information is recorded in the image recording section.
In this case, the cut sheet is sucked or stuck to an endless belt and thus conveyed to the image recording section by the belt-type conveying mechanism. Ink is then ejected from an ink-jet-recording-type recording head, such that the image information is recorded.
Furthermore, the image information recorded on the cut sheet by the image recording section is the image information on an original read by a scanner which is converted into an electric signal. This electric signal causes the ink-jet-type recording head to be driven, and the ink is then ejected from the recording head in the process of passing the cut sheet under the recording head on the belt conveying section, thereby achieving the recording.
In the image recording apparatus having such a configuration, a gap between the endless belt forming the belt conveying section and the recording head is set to be very small, for example, 1 mm or less. Thus, when the cut sheet has caused a jam error for some reason during a recording operation of the image information, it is necessary to evacuate the belt conveying section downward and provide a work area (space) to remove the jammed cut sheet. Moreover, when a recovery operation of the recording head is performed, it is necessary to provide a work area (space) required to insert a maintenance section because the maintenance section is pressed against a nozzle under the recording head.
On the contrary, as disclosed in, for example, Jpn. Pat. No. 2816217, a recording apparatus has been proposed which is provided with a support cancellation mechanism to separate a belt conveying section from a recording head substantially in parallel in order to secure a work area for Jam recovery between the belt conveying section and the recording head. That is, the belt conveying section is pivotally provided in a recording apparatus main body so that it pivots on a drive roller at one end where the endless belt is wound and hooked. In this configuration, when the cut sheet has caused jamming, the other end of the belt conveying section can be spaced from the recording head pivotally on the drive roller. Alternatively, a configuration has been proposed wherein a belt conveying section can ascend and descend while keeping in parallel with a recording head owing to an ascend/descend mechanism.
In this example, the recording head is composed of recording heads of four colors: black, yellow, magenta and cyan. Theses colors are arranged in series in a recording paper conveying direction. Thus, while recording paper is being conveyed from an upstream side to a downstream side by turning the endless belt, the four colors including black, yellow, magenta and cyan are superposed in order on the recording paper being conveyed, thereby forming a color image. In addition, such a recording head is held by a main body frame, and the ascendably/descendably configured belt conveying mechanism is also held to the main body frame via a link, an arm, etc.
On the other hand, if an attempt is made to obtain an image of a quality as high as photographic quality which has recently been needed by users, it is necessary to align the black, yellow, magenta and cyan recording heads arranged in series in the paper conveying direction, and to accurately set the distance between a surface to convey the recording paper and a surface to eject the recording head ink.
In the configuration of the recording apparatus described in Jpn. Pat. No. 2816217, the belt conveying section is vertically moved by the ascend/descend mechanism held by the main body frame so that the belt conveying section faces the recording head. Therefore, in this recording apparatus, if a slight deformation, distortion or the like is caused due to the vertical movement of the belt conveying section, it is not possible to maintain an accurate distance from the recording head to the belt conveying section, resulting in a significant decrease in the quality of a recorded image.
There is thus a desire for a belt conveying section with a strong configuration, i.e., one in which deformation does not occur. In such a configuration, the belt conveying section itself is increased in size and becomes significantly heavier. Consequently, frame rigidity is required to highly accurately position the belt conveying section and retain that position, which is not easy to achieve.
Thus, in the configuration of the recording apparatus in Jpn. Pat No. 2816217, the belt conveying section is vertically movable owing to the ascend/descend mechanism, such that the frame is loaded and the positional relation between the belt conveying section and the recording head cannot be reproduced as designed if even a slight deformation or distortion is caused during the transportation from a manufacturing site to an Installation site. There is therefore a problem of displacement which emerges in the superposing direction of colors of the ejected ink.